This invention relates to security systems using multiple receivers, and in particular to a method and system for allowing a receiver to monitor acknowledgement messages from another receiver to a common control panel to avoid unnecessary and duplicative message transmissions to that control panel.
The present invention addresses several problems found in large wireless security systems. The first problem is caused by wireless security systems that utilize a large number of wireless motion detector transmitters. When the security system is in the armed state, these motion detector devices are not activated due to the lack of people moving about in the protected premises. However, when the security system is in the disarmed state, these motion detector devices are constantly transmitting signals to the associated RF receivers due to their detection of people moving within the protected premises while the control panel is disarmed. Since the control panel is disarmed, these transmitted signals have no significance and are therefore discarded by the control panel. However, the frequent signal transmissions from these types of transmitters cause a large amount of unnecessary signal traffic on the wired communication bus connecting the control panel to the RF receivers. In effect, these unnecessary signal transmissions hamper the ability of the control panel to service signals transmitted from other devices, wired and wireless, which need immediate attention even when the system is disarmed.
It is therefore an object of the present invention to provide a wireless security system that overcomes the problems of the prior art mentioned above.
It is also an object of the present invention to provide such a security system that ameliorates the unwanted processing requirements on the control panel due to motion detector transmissions (and other non-essential transmissions) that occur during the system disarmed state.
In particular, it is an object of the present invention to provide such a security system that can process the received messages at the receiver module and filter the messages that originate from non-essential transmitters, so that such non-essential messages are not passed on to the control panel when in the disarmed state.
The second problem found in large wireless security systems relates to the use of a large number of wireless receivers in a system that are connected to the control panel. Although most currently available wireless security systems are limited to the use of not more than two receivers on a single system, it is desired to be able to use more receivers in larger premises. That is, this limitation is restrictive in relatively large systems where more than two RF receivers are necessary in order to properly detect signals from all of these transmitting devices distributed over a very wide area in the system. For example, in a six-story building containing, twenty transmitting devices per floor, it would be best to have one RF receiver located on each floor in order to avoid large amounts of RF transmission loss between multiple floors which are generally constructed of steel-enforced flooring materials. However, placing 6 RF receivers on the same security control""s communication bus makes it almost impossible for the control to differentiate between recent and previous transmission events from a given transmitting device or to identify a single transmission event reaching the control via each of some of the receivers at slightly different time intervals. This is further aggravated by the fact that in most wireless systems, a given transmission event involves the transmission of a multiple number of identical transmitted messages over a period of 2-4 seconds in order to ensure adequate reception by a given receiver. For example, it may be desirable to transmit messages in a sextet format, where the (usually) identical message is transmitted six times over the 2-4 second period to ensure proper reception by the control panel.
It is therefore a further object of the present invention to provide such a security system that allows the control panel to determine if a message is received out of sequence and to ignore its contents, accordingly.
The third problem found in large wireless security systems relates to the additional traffic generated on the control""s communication bus when a multiplicity of RF receivers are connected. In the above example using 6 RF receivers, a single sensor event could cause the generation of up to six identical messages to the control. These additional messages could cause the control""s communication bus to become overloaded.
It is therefore a further object of the present invention to provide such a security system that allows each receiver to monitor the transmissions between the control panel and the other receivers to determine if a message has already been transmitted to and acknowledged by the control panel and avoid repetitive transmissions to the control panel.
The fourth problem encountered relates to the tedious and time-consuming task required of the system installer in programming responses to be carried out by the control panel when it receives a message from a given transmitter in the system. That is, at the time of installation, the installer must assign a particular response type to a particular serial or identification number for each transmitter in the system. Examples of response type are fire, perimeter, entry/exit door, panic, interior (motion), and interior-follower (motion looking at the entry door). During the control panel programming, the installer will assign a panel fire response to the smoke detectors, a burglary response type to perimeter serial numbers, etc. In some control panels, there may be 256 zones that need to be programmed, which is time consuming and error prone.
It is therefore desired to provide a methodology whereby the control panel can determine the type of product from the received message and execute a response accordingly, without having to carry out programming for each transmitter as in the prior art.
The present invention, in a first aspect, is thus a method and apparatus for use in a security system that includes a number of wireless transmitters, at least one wireless receiver in wireless communication with the wireless transmitter(s), and a control panel connected to the wireless receiver(s). The receiver receives a wireless message from a transmitter and first determines if the system is in the disarmed mode. If it is in the disarmed mode, then the receiver determines the product type of the wireless transmitter from the wireless message. The receiver then determines from the transmitter product type if the transmitter is essential or non-essential. The receiver discards the wireless message if the transmitter is indicated to be non-essential, and it sends the wireless message to the control panel if the transmitter is indicated to be essential.
In accordance with this first aspect of the invention, the receiver determines if the system is in the disarmed mode by checking a system status bit in an internal memory location. The receiver determines from the product type of the received transmitted message if the message is essential or non-essential by checking the transmitter product type against a product type table in memory in the receiver. The product type table is loaded into memory in the receiver from a communications bus message previously sent by the control panel to the receiver.
The present invention, in a second aspect, is a security system and method of operating the security system which includes a wireless transmitter, two or more receivers in wireless communication with the wireless transmitter, and a control panel connected to the wireless receivers. The transmitter transmits a wireless message per event, such as the opening and closing of a door, which includes a unique transmitter identification number, a status portion with a plurality of status bits identifying the event, and a sequence count. Each receiver receives the wireless message, converts the wireless message to a digital message, and then sends the digital message to the control panel. The control panel then processes the digital message from each receiver by first extracting the sequence count and transmitter identification number from the message. A previous sequence count associated with the same transmitter identification number of a previous event is retrieved from memory, and the sequence count from the present message is compared with the previous sequence count retrieved from the memory. If the sequence count from the present message is less than the previous sequence count, then the control panel ignores the present message. If, however, the sequence count from the message is not less than the previous sequence count, then the control panel processes the message (i.e. the status bits) and replaces the previous sequence count in memory with the sequence count from the present message.
In further accordance with this second aspect of the invention, the transmitter prepares the message for wireless transmission to the receiver by first determining if any of the status bits in the status portion of the wireless message has changed from the previously transmitted message as a result of a new transmission event. If any of the status bits have changed, indicating a new transmission event, then the transmitter increments the sequence count from the previously transmitted message. If, however, none of the status bits has changed, indicating a repeated message of the same event, then the transmitter uses the same sequence count as in the previously transmitted message.
This second aspect of the invention thereby allows the control panel to determine if a message received from a certain transmitter is out of sequence due to delays in reception, processing, etc. by one of the receivers in the system.
The present invention, in a third aspect, is a security system and method of operating the security system which includes a wireless transmitter, a plurality of wireless receivers in wireless communication with the wireless transmitter, and a control panel connected to the wireless receivers via a data communications bus. A first receiver receives a first wireless message, converts the first wireless message to a first digital message, and then sends the first digital message to the control panel. A second receiver receives a second wireless message, converts the second wireless message to a second digital message, and places the second digital message in an output buffer for subsequent transmission to the control panel. The control panel receives the first digital message from the first receiver, and then sends an acknowledgement message on the data bus indicating that the first digital message has been successfully received. The second receiver monitors data transmissions on the data communications bus from the control panel, and upon detecting the acknowledgement message on the data communications bus, determines if the acknowledgement message indicates that first digital message received by the control panel is identical to the second digital message in its output buffer. If the acknowledgement message indicates that first digital message received by the control panel is identical to the second digital message in its output buffer, then the message in the output buffer is discarded. If, however, the acknowledgement message indicates that first digital message received by the control panel is not identical to the second digital message in its output buffer, then the second digital message is sent from its output buffer to the control panel.
In a fourth aspect, the present invention is a security system that has a plurality of wireless transmitters, a wireless receiver in wireless communication with the wireless transmitters, and a control panel connected to the wireless receiver. A wireless message, which includes a transmitter product type, is received from the wireless transmitter. The control panel extracts the transmitter product type from the wireless message and then determines a response type to be performed as a function of the transmitter product type extracted from the wireless message. A response to the wireless message is then executed in accordance with the determined response type. The response type may be determined by the control panel by using the transmitter product type to lookup an associated response type in a response type table at the control panel. The wireless message also includes a unique identification number, and the transmitter product type may be a separate field from the unique identification number or it may be integral with the unique identification number. The unique identification number is initially programmed in the wireless transmitter by assigning the product type portion as a function of the transmitter type.